American Express, which has long been known for catering to high-end consumers, is moving downmarket. They’ve got a new platform called Serve, which is kind of a catchall service that supports many payment methods from traditional plastic cards with magnetic stripes to NFC to QR codes to basic online payments. The partnership with Zynga is meant to onboard new Amex customers and could give the credit card company the so-called FarmVille demographic.

“Zynga has a very large customer base,” said David Messenger, American Express’ executive vice president of enterprise growth. “This partnership isn’t for existing credit and charge card customers. It’s about trying to appeal to a new segment. These customers may be Millennials. They may be somewhat underserved in terms of banking. They may only use debit, cash and check.”

FarmVille players will be able to plant an American Express-branded tree in their farms. If they plant the virtual tree, they’ll be nudged to register for a prepaid card and American Express’ Serve program. Then after that, they can add money to their Serve account and activate the card.

The first five purchases of $25 or more with the card will earn users extra Farm Cash. Other rewards will probably be added later on and the program will probably eventually include more games too.

Zynga’s chief marketing and revenue officer Jeff Karp says whatever revenues the American Express deal brings will fall in under advertising. He didn’t say how much revenue the Amex deal might represent. About 8.7 percent of Zynga’s $321 million in revenue last quarter came from advertising. The rest came from virtual goods.

“This deal highlights how we can bring brands to life,” he said. “We’re blurring the lines between real world and virtual world.”